Alex building an eyewall, still not a hurricane

By: Dr. Jeff Masters , 7:34 PM GMT on June 29, 2010

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Tropical Storm Alex is slowly building an eyewall, which is now more than 50% complete, according to recent satellite imagery and microwave images (Figure 1.) Satellite loops show a slot of dry air is spiraling into the center of the storm, and until this dry slot gets closed off, Alex will not be able to intensify significantly. Alex's heavy thunderstorms and low level spiral bands continue to slowly increase, but upper-level outflow is mediocre to the north and east, and absent elsewhere. The Hurricane Hunters are in the storm and have not found any hurricane-force winds at the surface yet.


Figure 1. Microwave "radar in space" image taken at 10:11 am CDT Tuesday June 28, 2010, showing that Alex had built an eyewall a little more than 50% complete. Image credit: Navy Research Lab.

Impacts
Alex is already bringing bands of heavy rain to the coasts of Texas and Mexico, as seen on the Brownsville, Texas radar. Hurricane local statements with projections for how Alex will affect the coast are now being issued by the National Weather Service in Brownsville and Corpus Christi. Since Alex is a large storm, it will have a storm surge that will affect most of the South Texas coast. NHC is giving a 40% - 60% chance of a storm surge of at least 3 feet affecting the Brownsville area, and 10% - 30% chance the surge will exceed 5 feet. In theory, a Category 2 hurricane moving WNW at 5 mph can bring a storm surge of up to 8 - 9 feet to the South Texas coast (Figure 2.) However, Alex is now unlikely to get that strong, and the surge should be less. Flooding damage from the expected 6 - 12 inches of rain from Alex will also be a major concern, as will wind damage. The combined wind, surge, and flooding damage from 2008's Hurricane Dolly, which hit near Brownsville, were about $1.05 billion. Dolly was a Category 2 hurricane offshore that weakened to a Category 1 hurricane with 85 mph winds when it made landfall. I expect Alex will be similar in its impacts to Dolly, though Alex's storm surge damage is likely to be greater. If Alex hits more than 50 miles south of the Texas border, as currently appears likely, the damage will be far less, since this region of the coast is relatively sparsely populated.


Figure 2. Maximum Water Depth (storm tide minus the elevation of the land it is passing over) computed using the primary computer model used by the National Hurricane Center (NHC) to forecast storm surge--the Sea, Lake, and Overland Surge from Hurricanes (SLOSH) model. The accuracy of the SLOSH model is advertised as plus or minus 20%. The "Maximum Water Depth" image shows the water depth at each grid cell of the SLOSH domain. Thus, if you are inland at an elevation of five feet above mean sea level, and the combined storm surge and tide (the "storm tide") is ten feet at your location, the water depth image will show five feet of inundation. This Maximum of the "Maximum Envelope of Waters" (MOM) image was generated for high tide, and thus shows the worst-case inundation scenarios for a mid-strength Category 2 hurricane moving WNW at 5 mph. For more information on storm surge, consult our detailed storm surge pages.

Track forecast for Alex
The latest 12 UTC (7am CDT) runs of our most reliable computer models confirm the faster movement of Alex to the coast, and residents in the affected areas now have 12 hours less to prepare for Alex's arrival than it seemed with yesterday's forecasts. Conditions will begin to deteriorate along the coast late tonight, so today is the day to finish preparations if you live near the Texas/Mexico border! The ridge that is steering Alex to the northwest is expected to strengthen today and Wednesday, which should push Alex on a more west-northwest and then westerly track on Wednesday. A few models even have Alex moving west-southwest by the time it makes landfall. The most northerly landfall location, near Brownsville, is predicted by the HWRF model.

To get the probability of receiving tropical storm force winds or hurricane force winds for your location, I recommend the NHC wind probability forecasts. The 4am CDT (9 UTC) wind probability product predicted that Brownsville, Texas had the highest odds of getting a direct hit from Alex:

Brownsville, TX: 88% chance of tropical storm conditions (winds 39+ mph), 23% chance of hurricane force winds (74+ mph). This is the cumulative probability through Saturday morning. The wind probability forecasts also include separate probabilities for each 12-hour period between now and three days from now, and each 24 hours for the period 4 - 5 days from now.

Corpus Christi, TX: 42% tropical storm, 1% hurricane.

La Pesco, MX: 37% tropical storm, 3% hurricane.

Freeport, TX: 18% tropical storm, 0% hurricane.

Tampico, MX: 14% tropical storm, 0% hurricane.

Galveston, TX: 13% tropical storm, 0% hurricane.

Intensity forecast for Alex
Alex is over a region of ocean with a warm, clockwise rotating Loop Current eddy that broke off from the Loop Current in July 2009 and moved west-southwest over the past 11 months. This eddy has moderately high total ocean heat content . Wind shear has fallen to a low 5 knots, and is projected by the SHIPS model to remain in the low range, below 10 knots, this afternoon and Wednesday. The combination of low wind shear and moderately high ocean heat content should allow Alex to intensify into a Category 1 hurricane, but time is running out for it to be a Category 2 hurricane. NHC is giving Alex a 79% chance of being a hurricane on Wednesday morning, and a 4% chance it will be a major hurricane at that time. Water vapor satellite images show the amount of dry air over the western Gulf of Mexico has decreased over the past day, though as I noted above, the dry slot wrapping into Alex's core is currently keeping the storm from closing off an eyewall. Dry air may turn out to be an increasing detriment to Alex on Wednesday as the storm approaches land. Another factor limiting Alex's intensification may be that the atmosphere is more stable than usual right now--temperatures at 200 mb are a rather warm -50°C, and are expected to warm an additional 1 - 2 degrees by Wednesday. I don't expect Alex to stall out again, so slow motion leading to upwelling of cold water will probably not be a problem for Alex. The main issue limiting intensification will be the fact that Alex is so large, and it takes more time for a large storm to organize. Thus, I think Alex has only a 10% chance of intensifying into a major hurricane before landfall.

Elsewhere in the tropics
The last few runs of the NOGAPS model have been predicting the formation of a tropical disturbance off the coast of Nicaragua on Friday or Saturday that will move northwestward towards western Cuba. The GFS model, and the two models that use it for starting conditions, the GFDL and HWRF, are indicating the possibility that a weak extratropical storm may form along coastal Alabama this weekend. It is unlikely that such a storm would be over water long enough to transition to a tropical storm.

Wind and ocean current forecast for the BP oil disaster
It currently appears that Alex's winds will not directly affect the oil slick location. However, because Alex is such a deep low pressure region, strong southeast to south winds of 10 - 20 knots will blow over the oil slick region today through Thursday, according to the latest marine forecast from NOAA. The resulting currents should act to push oil to the west and northwest onto portions of the Louisiana, Mississippi, and Alabama coasts, according to the latest trajectory forecasts from NOAA and the State of Louisiana. Oil will also move westward along the central Louisiana coast towards the Texas border. Alex is currently bringing swells of 3 - 4 feet to the coastal regions impacted by the oil slick, and these swells will increase to 6 - 8 feet on Wednesday. Wave heights will increase to 5 - 7 feet on Wednesday. Alex is expected to bring a storm surge of 1 - 2 feet along the coast in the oil spill region. The swells and waves that will accompany these high water levels will act to push oil deep into the marshlands in some locations. The long range forecast for the oil slick region is uncertain, due to the possibility a weak area of low pressure might develop late this week along the remains of a cold front draped across the region.

Resources for the BP oil disaster
Map of oil spill location from the NOAA Satellite Services Division
My post, What a hurricane would do the Deepwater Horizon oil spill
My post on the Southwest Florida "Forbidden Zone" where surface oil will rarely go
My post on what oil might do to a hurricane
NOAA's interactive mapping tool to overlay wind and ocean current forecasts, oil locations, etc.
Gulf Oil Blog from the UGA Department of Marine Sciences
Oil Spill Academic Task Force
University of South Florida Ocean Circulation Group oil spill forecasts
ROFFS Deepwater Horizon page
Synthetic Aperture Radar (SAR) imagery from the University of Miami

"Hurricane Haven" airing again this afternoon
Tune into another airing of my live Internet radio show, "Hurricane Haven", at 4pm EDT today. Listeners will be able to call in and ask questions. The call in number is 415-983-2634, or you can post a question in the comments area on my blog during the show. You can also email the questions to me today before the show: jmasters@wunderground.com. Be sure to include "Hurricane Haven question" in the subject line. Some topics I'll cover today on the show:

1) Alex
2) A look ahead at what may happen the rest of hurricane season

Today's show will be about 45 minutes, and you can tune in at http://www.wunderground.com/wxradio/wubroadcast.h tml. The show will be recorded and stored as a podcast.

Next post
I'll have an update Wednesday morning by 9:30am CDT. Rob Carver is planning on doing a late-night update tonight.

Jeff Masters

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1043. Patrap
Member Since: Posts: Comments:
It would be pretty pointless to upgrade Alex just to have recon find 70mph winds again.

Thats why they wait.
Member Since: June 9, 2007 Posts: 4 Comments: 15891
Quoting RecordSeason:
1008:

Wrong. That is a feeder band that sheared off of Alex. You can still see counter clockwise motion in the low levels.

It definitely is part of Alex

What's the matter with you? Talking about a future system. And no, Alex didn't give us 30 knot winds...

Might try to figure out what you're talking about before the instant, atmo is wrong thing. I've been wrong plenty of times, but cannot recall a case of you being right about anything, yet. Maybe with hard work [snip, gets rough from here on].
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1040. CJC111
Do you guys think the the track will be brought even further south or is the west heading a wobble that will go a little more NW?
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Quoting HurricaneSwirl:


I know that, but why would it be lower than it was previously?


Probably because the cloud temperature in the center region is warming, went from ~ -57 to ~ -53.
Member Since: September 23, 2005 Posts: 14 Comments: 11166
Quoting kmanislander:


Looks like W to me.
I read somewhere today(I don't know if it was on here or NHC) that models were initializing a tropical system east of Nicaragua on Friday heading towards western Cuba. You know anything about that ?
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1037. Patrap
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Takin them longer than usual to get the 8 PM stuff out, probably because of the decision whether to up Alex or not. (probably won't do so until after the recon)
Member Since: July 7, 2008 Posts: 2 Comments: 3237
Quoting Orcasystems:


huh??

The NHC probably won't upgrade it to a hurricane until the recon can prove it is. The recon isn't in the center yet.
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1033. txjac
I love Veracruz, spent about a month there
Member Since: April 24, 2010 Posts: 1 Comments: 2523
ugh this has a 980mb and its olny a TS come on this is a hurricane
Member Since: May 21, 2006 Posts: 5091 Comments: 115107
Cloud signature has become a bit ragged.

Member Since: June 9, 2007 Posts: 4 Comments: 15891
Quoting Kristina40:


Whatever did it, it's drenching us here in Panama City. We needed a cooling off anyhow, maybe some of my blossoms will set with the sub 90 degree temps this week.
Oh, not yet. The extra-trop system gets dropped off by the approaching trough from the north in a few days, according to a couple of models.

So, on the N gulf, the winds should lay down for a day or so and pick back up, and moreso, from this.
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1029. Patrap
ESL by LSU Low Cloud Product
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Quoting katadman:


Good for you. Where were you doing your grad studies? In ag?


Yes a form of Ag, Fish Farming :) Studied the Mexican catfish and shrimp farms between Matamoros and Veracruz. Lived in La Pesca. Hope to go back and get an Organic Tilapia farm going sometime soon, after the drug wars wind down.
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1027. Patrap



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Quoting Stormchaser2007:
Alex wont be declared a Hurricane probably until the 11pm advisory.
That's what I was saying earlier. The NHC wants to review and analyze the information provided by recon to make the call.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
It's the signature of the eye pressure difference pulling the clouds down.
Member Since: August 11, 2008 Posts: 0 Comments: 2315
Quoting CybrTeddy:
Just ignore the ADT's weakening flag, always does that with every storm no matter what phase of organization. Heck, even did it with Hurricane Gustav as a 150 mph hurricane.
Convection waned a bit...

warmer cloud tops:
Member Since: Posts: Comments:
Quoting Ameister12:
James Franklin from the NHC says that they will probably keep Alex a tropical storm because they want the recon to give the information and they probably won't get there by the 8.


UR KIDDING ME!? >:O
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Alex wont be declared a Hurricane probably until the 11pm advisory.
Member Since: June 9, 2007 Posts: 4 Comments: 15891
Ridiculous. Alex does not fit on the "western atlantic" satellite anymore. Outflow bands go off the SW and N sides of it.


Compare this to just 5 days ago at 7pm...
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Quoting atmoaggie:
Different storm. Extra-trop system, broad area of 30 knot winds, onshore in the NE gulf. Alex didn't do that...


Whatever did it, it's drenching us here in Panama City. We needed a cooling off anyhow, maybe some of my blossoms will set with the sub 90 degree temps this week.
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1018. Patrap
tropicalatlantic.com
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Quoting Snowlover123:


NYC and the rest of the Mid Atlantic was hotter than the southeast. Be glad you're down there! Although... we are getting a refreshing break in the next few days...


well it's only gonna get hotter here. No offense, but we've had heat indices over 100 for a month straight. Glad you guys will be getting some relief though, that kinda heat is just miserable!!
Member Since: Posts: Comments:
Quoting Ameister12:
James Franklin says that they will probably keep Alex a tropical storm because they want the recon to give the information and they probably won't get there by then.


huh??
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Hello all. New here, but I was present when Dolly was predicted to hit Mexico as a weak Cat.1, then did a little side-step and slammed us here in Port Mansfield with sustained 100/gusts 120 for 9.5 hours. Despite all of the westward predictions, we are certainly taking precautions. (It's a bit dramatic here this pm.) Let's hope west is real as the farmers have much at stake...scrambling to harvest as we speak. Thanks.
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Member Since: June 9, 2007 Posts: 4 Comments: 15891
James Franklin from the NHC says that they will probably keep Alex a tropical storm because they want the recon to give the information and they probably won't get there by the 8 o'clock advisory.
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HH inbound :)



AOI

AOI

AOI

Hurricane Hunter Data

TS BUSTED FORECAST ALIBI
Member Since: Posts: Comments:
Quoting AstroHurricane001:


This storm ALREADY takes up the entire Gulf, except for a dry slot near Cuba.
Different storm. Extra-trop system, broad area of 30 knot winds, onshore in the NE gulf. Alex didn't do that...
Member Since: Posts: Comments:
Quoting JLPR2:


O_O Pinhole eye, *drools on laptop screen*
haha! XD


LMAO!
Member Since: April 1, 2010 Posts: 9 Comments: 2699
Quoting StormW:
Barometer Bob is having another broadcast tonight at 8:00 pm. He has asked me to call in again at 8:30.


sweet storm! I'll be listening in :)
Quoting Baltimorebirds:
The weather channel just reported that south pare island is giving voluntary evacuations for the coast.


Yeah, and mandatory evacuation for high profile vehicles and RVs.
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1001. JLPR2
11:41 PM GMT on June 29, 2010
Quoting MiamiHurricanes09:
Watch in a matter of hours people are just going to be throwing out the "Pinhole eye" concept, lol.


O_O Pinhole eye, *drools on laptop screen*
haha! XD
Member Since: September 4, 2007 Posts: 7 Comments: 8698
1000. HurricaneSwirl
11:41 PM GMT on June 29, 2010
Wow, usually at that point they are still finding 1000+ pressures. This time they descended right into ~995 mb!
Member Since: July 7, 2008 Posts: 2 Comments: 3237
999. MiamiHurricanes09
11:41 PM GMT on June 29, 2010
Quoting StormW:
Barometer Bob is having another broadcast tonight at 8:00 pm. He has asked me to call in again at 8:30.
Awesome! Looking forward to it.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
998. Snowlover123
11:41 PM GMT on June 29, 2010
Quoting StormChaser81:
Eyewall is almost complete, if not 100% done. You can see it on the water vapor. It's going to be a small eye (5-10 miles or so wide).



Doesn't look like an eye on the Water Vapor loop.
Member Since: April 1, 2010 Posts: 9 Comments: 2699
997. MiamiHurricanes09
11:40 PM GMT on June 29, 2010
Quoting StormChaser81:
Eyewall is almost complete, if not 100% done. You can see it on the water vapor. It's going to be a small eye (5-10 miles or so wide).

Watch in a matter of hours people are just going to be throwing out the "Pinhole eye" concept, lol.
Member Since: September 2, 2009 Posts: 130 Comments: 21193
995. cooldayr
11:40 PM GMT on June 29, 2010
On your marks, get set, start f5ing
Member Since: June 18, 2010 Posts: 0 Comments: 18
994. MrstormX
11:40 PM GMT on June 29, 2010
Important point, people live in Mexico also... just because it is not a U.S. landfall doesn't mean it is insignificant.
Member Since: May 27, 2009 Posts: 0 Comments: 4438
993. Tazmanian
11:40 PM GMT on June 29, 2010
not even there yet and it found this


23:26:00Z 24.883N 95.550W 579.3 mb
(~ 17.11 inHg) 4,635 meters
(~ 15,207 feet) 994.7 mb
(~ 29.37 inHg) - From 51° at 39 knots
(From the NE at ~ 44.8 mph) 4.0°C
(~ 39.2°F) -1.2°C
(~ 29.8°F) 41 knots
(~ 47.1 mph) - - - -
23:26:30Z 24.867N 95.600W 604.1 mb
(~ 17.84 inHg) 4,314 meters
(~ 14,154 feet) 996.6 mb
(~ 29.43 inHg) - From 59° at 42 knots
(From the ENE at ~ 48.3 mph) 5.6°C
(~ 42.1°F) -0.2°C
(~ 31.6°F) 43 knots
(~ 49.4 mph)
Member Since: May 21, 2006 Posts: 5091 Comments: 115107

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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.